Rapid Microwave-Assisted Transesterification of Palm Oil Using Sulfonated Graphene Catalyst Prepared Via SLS-Stabilized Turbulence-Assisted Shear Exfoliation

Abstract

Graphene-based sulfonated catalysts (graphene–SO₃H) were synthesized using the turbulence-assisted shear exfoliation (TASE) method with sodium lauryl sulfate (SLS) as a stabilizing agent. The catalyst was applied for microwave-assisted transesterification of palm oil to produce biodiesel. Characterization of the catalyst via FTIR, XRD, and SEM-EDX confirmed the successful sulfonation and the formation of a porous graphene structure. Among the tested condition, the highest biodiesel yield of 99.07% was achieved using 2 mL SLS and 0.54 g graphene-SLS within 3 min at 65°C. The resulting product met the density and pH requirements, with values of 0.89 g/mL and approximately 7.4, respectively. However, its viscosity of 8.38 cS) and acid number of 1.28 mg KOH/g exceeded the limits set by EN 14214, indicating that the product should still be regarded as crude biodiesel rather than standard-compliant fuel-grade biodiesel. Therefore, further post-reaction purification is required to reduce residual impurities affecting viscosity and acid value. This study demonstrates that the combination of graphene–SO₃H catalyst and microwave irradiation is promising as a rapid transesterification route for palm-oil-based biodiesel production, while product purification remains essential for fuel-grade application.